1. Field of the Invention
The present invention relates to a method for double patterning a thin film on a substrate, and more particularly to a method for double patterning a thin film on a substrate using a developable anti-reflective coating (ARC) layer.
2. Description of Related Art
In material processing methodologies, pattern etching comprises the application of a thin layer of light-sensitive material, such as photo-resist, to an upper surface of a substrate that is subsequently patterned in order to provide a mask for transferring this pattern to the underlying thin film on a substrate during etching. The patterning of the light-sensitive material generally involves exposure by a radiation source through a reticle (and associated optics) of the light-sensitive material using, for example, a photo-lithography system, followed by the removal of the irradiated regions of the light-sensitive material (as in the case of positive photoresist), or non-irradiated regions (as in the case of negative resist) using a developing solvent. Moreover, this mask layer may comprise multiple sub-layers. 
More recently, a double patterning approach has been introduced to allow the patterning of smaller features at a smaller pitch than what is currently possible with standard lithographic techniques. One approach to reduce the feature size is to use standard lithographic pattern and etch techniques on the same substrate twice, thereby forming larger patterns spaced closely together to achieve a smaller feature size than would be possible by single exposure. During double patterning, the substrate is exposed to a first pattern, the first pattern is developed in the light-sensitive material, the first pattern formed in the light-sensitive material is transferred to an underlying layer using an etching process, and then this series of steps is repeated for a second pattern.